Such materials are of interest in very varied fields of applications, which are all those of known metal phosphides. Notably, the following may be mentioned: magnetic ferro-magnet applications for MnP and FeP; hydrodesulfurization catalyst applications for Ni2P; luminescent materials compatible with biological media; microelectronics and optoelectronics for InP; and electronics for GaP. The latter two phosphides are also used in the photovoltaic energy field.
Various methods of synthesis have been proposed hitherto for synthesizing metal phosphides, including FeP, MnP, Ni2P, PtP2, InP and GaP, using synthesis intermediates and generally proposing a double thermolysis of a metal precursor and a phosphorus atom donor.
Thus, the synthesis of Ni2P may be mentioned, which comprises the thermal decomposition of Ni(acac)2 at 210° C. and then the reaction with a P(n-octyl)3 phosphine compound at 330° C. This temperature of 330° C. is necessary for the decomposition of P(octyl)3 which serves as a “phosphorus atom donor by breaking phosphorus-carbon bonds” as described in the publication “Generalized Synthesis of Metal Phosphide Nanorods via Thermal Decomposition of Continuously Delivered Metal-Phopshine Complexes Using a Syringe Pump” by Jongman Park, Bonil Koo, Ki Youl Yoon, Yosun Hwang, Misun Kang, Je-Geun and Taeghwan Hyeon, J. Amer. Chem. Soc. 127, 8433-8440 (2005). No control of the stoichiometry is therefore possible (P(n-octyl)3 is used as solvent for the reaction). It is therefore possible to obtain only the MxPy phase stable at this temperature, namely Ni2P in this case.
In the case of Pt (which is in the same column as Ni), this synthesis results in PtP2, and therefore an inverse stoichiometry. Thus, it is not possible with this type of method to obtain a compound of different stoichiometry.
FeP and MnP syntheses follow a similar principle. The method is limited by the temperature of decomposition of P(n-octyl)3, which is above 330° C.
As regards the synthesis of InP, it is known to carry out the thermal decomposition of various indium precursors of the CpIn (Cp=cyclopentadienyl), Cp*In (where Cp*=pentamethylcyclopentadienyl) or In(C(CH3)3)3 type into In(0) nanoparticles followed by a reaction with P(SiMe3)3, which precursor is hydrolyzed in situ to PH3, as described in the publication “Growth of InP Nanostructures via Reaction of Indium Droplets with Phosphide Ions: Synthesis of InP Quantum Rods and InP—TiO2 Composites” by Jovan M. Nedeljkovic, Olga I. Micic, S. Philip Ahrenkiel, Alex Miedaner and Arthur J. Nozik, J. Amer. Chem. Soc. 126, 2632-2639 (2004). The compound P(SiMe3)3 is not only very expensive, as its synthesis is tricky and extremely dangerous, but it also hydrolyzes very easily in air to PH3, which is an extremely toxic substance (fatal in a very low concentration in air: CL50 [ppm/1 h]=20).